1. Field of the Invention
The present invention relates generally to tape cassette reels and more particularly to a tape cassette reel having wound therearound a magnetic tape and which is incorporated in a video tape cassette.
2. Description of the Prior Art
In order to gain a better understanding of the present invention, let us first explain a known tape cassette reel with reference to FIGS. 1 and 2 (see Japanese Patent Published Gazette No. 63-184979 and corresponding U.S. application Ser. No. 145,391). This previously-proposed tape cassette reel has a magnetic tape wound therearound and is incorporated in a video tape cassette.
Referring to a perspective view forming FIG. 1 and a side view of a section forming FIG. 2, it will be seen that a tape cassette reel TR is comprised of a reel hub 1 formed as one body with a lower flange portion 2 and an upper flange portion 5 secured to the upper end face of the reel hub 1. The upper flange portion 5 is comprised of a central portion 3 made of an opaque material of a desired color and an outer peripheral flange portion 4 made of a transparent, synthetic resin such as acrylonitrile butadiene styrene copolymer (ABS) resin, so-called SAN resin and the like according to the so-called dichromatic molding method.
The outer surface of the colored central portion 3 of the upper flange portion 5 is made lower, as viewed in the figure, than the outer peripheral flange portion 4 by a very small amount. An aperture 6 is formed through the central portion 3 of the flange portion 5 at its central portion, and a center pin 7 is loosely supported between the central, lower surface 3 of the upper flange portion 5 and the central, upper end face of the reel hub 1. The center pin 7 comes in contact with cassette reel pushing springs S provided in a cassette housing C shown in FIG. 3. Upon molding, a pouring gate mark g is formed between the aperture 6 and the outer peripheral flange portion 4. Protruding portions 4a, 4a are formed on the inner peripheral side of the transparent, outer peripheral flange portion 4 of the upper flange portion 5 so as to protrude in the radially central direction of the colored central portion 3. Two pouring gate mark g are also formed on the outer surfaces of these protruding portions 4a, 4a, and these pouring gate mark g are formed in the molding-process for molding the transparent, outer peripheral flange portion 4.
As shown in FIG. 2, a hub drive shaft engaging aperture 9 is formed on the lower surface side of the reel hub 1 so that it can be engaged with a hub drive shaft of a video tape recorder body (not shown). As shown in FIG. 1, a clamp piece engaging portion 8 is formed around the peripheral surface of the reel hub 1. The clamp piece engaging portion 8 is used to fix the end of a video tape (not shown) thereto together with a clamp piece (not shown). Reel brake engaging teeth 2a are formed around the outer peripheral surface of the lower flange portion 2. Then, the upper flange portion 5 is welded at the lower surface of the colored central portion 3 thereof to the upper end face of the reel hub 1 by an ultrasonic welding-process, thereby completing the tape cassette reel.
In the above-mentioned tape cassette reel according to the prior art, the protruding portions are formed on the inner peripheral side of the outer peripheral flange portion so as to protrude toward the inside of the colored central portion, and the pouring gate mark are formed on the outer surfaces of the protruding portions. Thus, when the outer peripheral flange portion of the upper flange is molded by a molding-process, resin flows from the protruding portions to the inner peripheral portion of the upper flange portion and then spreads to the outer peripheral side in a two-stage fashion, degrading the efficiency of the resin flow.
After the molding-process, the marks of the pouring gates remain on the outer surfaces of the protruding portions of the outer peripheral flange portion which is protrusively molded with the colored central portion, deteriorating the quality of the external appearance of the tape cassette reel. If the tape cassette reel is very small, just like a tape cassette reel for a tape cassette of 8 mm video tape recorder, the marks of the pouring gates become very conspicuous so that the users feel as if they had bought an inferior product.